First clinical trial of a vaccine against the Ebola Bundibugyo strain begins in the DR Congo

Trial begins at the epicentre of the outbreak

The first clinical trial of an Ebola vaccine during the ongoing outbreak in the Democratic Republic of the Congo began on Friday, the head of the World Health Organization Tedros Adhanom Ghebreyesus said. The first dose was administered in Bunia, the capital of the north-eastern province of Ituri, which is the epicentre of the outbreak. “Science gives us hope. Today in Bunia, DR Congo, the first participants were vaccinated in a new Ebola vaccine trial called Tumaini, which means ‘hope’ in Swahili,” he wrote on X. According to him, the trial will help determine whether the candidates developed for the Bundibugyo virus work, while the existing Ervebo vaccine will be tested for now. “WHO supports these DR Congo-led efforts to find answers and save lives,” he added.

The scale of the outbreak and the challenge of the Bundibugyo strain

The worst Ebola outbreak in the history of the DR Congo has surpassed 9,700 cases, with the death toll exceeding 4,600. Among the many challenges of the epidemic response is the absence of any approved vaccines or treatments for the Bundibugyo species causing the epidemic. The Ervebo vaccine, approved against the more common Zaire strain, will be tested in a full-scale human trial to find out whether it provides cross-protection against Bundibugyo.

Trial design and vaccine candidates

The Tumaini trial is a single platform capable of assessing the safety, efficacy and immunogenicity of several vaccines at once. A ring vaccination approach is used — immunising contacts at high risk of infection. Two Bundibugyo-specific candidates are preparing to join the trial, currently undergoing earlier and smaller clinical trials: the adenoviral vector vaccine ChAdOx1, developed by the University of Oxford, and a product based on mRNA technology from the American company Moderna. Both have received funding from the Coalition for Epidemic Preparedness Innovations (CEPI) and, according to CEPI, are expected to enter the trial “in the near future”. Pregnant women and children aged 12 and older will be included in the trial — data for population groups that are usually excluded from clinical studies.

Significance and context

WHO emergencies director Chikwe Ihekweazu said the trial was designed to generate rigorous evidence on whether the participating vaccines can protect people at risk. “If successful, this will be the first time we have clear evidence of a vaccine’s efficacy against the Bundibugyo virus — a major step that could change our response to this outbreak and our preparedness for future ones,” he said. Steve Ahuka-Mundeke, head of the DR Congo’s epidemic response, called the inclusion of the trial in the outbreak response an important step towards meeting the urgent needs of affected communities. Ebola, transmitted through contact with bodily fluids and causing haemorrhagic fever, has killed more than 15,000 people in Africa over the past 50 years. The DR Congo declared its 17th Ebola outbreak on 15 May, and two days later WHO activated the public health emergency of international concern regime — the highest but one level of alert. Editorial comment: the event matters because there are still no approved vaccines or treatments against the Bundibugyo strain behind the current outbreak, which has caused more than 4,600 deaths; the trial directly tests whether the already approved Ervebo can provide cross-protection. In practical terms, the trial’s results will determine which tools medics in Ituri will have in this and future Bundibugyo outbreaks.